1. Field of the Invention
This invention relates to a laminated board lined with an electrically conductive material such as copper or aluminum, and being excellent in its heat conductivity, dimensional stability, heat resistance, and electrical characteristics.
2. Description of the Prior Art
As the material for printed circuit wiring, there has so far been used a laminated board made up of a prepreg sheet obtained by subjecting a base material such as paper, polyester cloth, glass fiber cloth, etc. to impregnation treatment with a thermosetting resin such as phenolic resin, epoxy resin, and so on; and a copper foil laminated on the thus obtained prepreg sheet.
As the representative material for the printed circuit wiring board, there can be exemplified a paper/phenolic resin board which is manufactured by bonding a copper foil to the laminated board of paper and phenolic resin with use of adhesive agent; and a glass/epoxy resin board which is manufactured by laminating a copper foil onto a prepreg sheet of glass base material and epoxy resin, and shaping the laminate into a desired shape. Both these laminated boards possess excellent characteristics in their performance and can be manufactured at a low cost, hence they occupy an important position as the raw material for the printed circuit wiring board. While the paper/phenolic resin board is somewhat inferior to the glass/epoxy resin board in the aspect of its performance, it is a favorable material in the aspect of its manufacturing cost.
Also, since the epoxy resin/glass board is excellent in its mechanical strength, heat resistance, dimensional stability, and others, it finds its use as the substrate material for the printed circuit wiring board having high packaging density, and also as the substrate material for the multi-layered printed circuit wiring board.
However, in view of strong demand, in recent years, for a more reduced size, higher performance, and, moreover, longer service life of electronic parts and electronic appliances, high integration in the electronic parts has progressed greatly, and remarkable development in the high density packaging has been attained in the packaging technique. With progress and development in these high integration and high packaging techniques, the present situation is such that the printed circuit wiring board has also been required to have high performance. For instance, with increase in the packaging density, thinning of the circuit wiring pattern and multi-layered technique of the base board have been the important problems. Further, with progress in the high density packaging, those electronic parts are required to have improved heat dissipation characteristics, on account of which the printed circuit wiring board should have high heat conductive property. In order for the copper-lined laminated board for the printed circuit wiring to fulfil the above-mentioned requirements, there are some points of problem which cannot be overcome by the performances of the above-described conventional paper/phenolic resin board and glass/epoxy resin board. For instance, in the case of the paper/phenolic resin board, since the base material is of paper, its heat resistant property is poor, and, moreover, when manufacturing the substrate for the multi-layered printed circuit wiring board, the dimensional stability becomes a problem. Further, since the paper/phenolic resin board requires an adhesive agent when it is fastened together with the copper foil, it accompanies a disadvantage in the fabrication of the multi-layered printed circuit wiring board. On the other hand, the glass/epoxy resin board is excellent in its heat-resistant property of the base material and yet the adhesive strength between epoxy resin and the copper foil are excellent, on account of which the board is said to be useful for the thinning of the circuit wiring pattern and as the substrate material for the multi-layered printed circuit wiring board, although it still has many points to be improved for satisfying the above-mentioned requirements. For example, as to its heat conductivity, the heat conductivity of the glass base material is in a range of from 0.6 to 1.0 Kcal/m.hr..degree. C. or so, while that of the thermosetting resin such as epoxy resin, polyimide resin, etc. is in a range of from 0.2 to 0.3 Kcal/ m.hr..degree. C. On account of this, it is impossible for the laminated shaped article as the composite product of both glass and thermosetting resin materials to attain its heat conductivity greater than that of the glass base material. In the substrate of the printed circuit wiring board for the high density packaging, it is a grave disadvantage that the printed circuit wiring board having the upper limit value of the heat conductivity of only 1 Kcal/m.hr..degree. C. or lower can be manufactured, in spite of the printed circuit wiring board being required to function as the heat dissipating board for electronic parts. Further, as for its dimensional stability, the glass base material is usually made of glass fiber cloth, owing to which it has anisotropy in its dimensional stability. Improvement in this property is therefore indispensable in the fabrication of the multi-layered printed circuit wiring board. In other words, a laminated shaped material having excellent isotropy and dimensional stability is needed.